Zhang Ming-hua

Application of microwave digestion in determination of the total nitrogen and phosphorus in wetland plants

This article reported the best conditions for plant sample microwave digestion using sulfuric acid-hydrogen peroxide (H<inf>2</inf>SO<inf>4</inf> - H<inf>2</inf>O<inf>2</inf>) technology with the closed vessel microwave digestion system and pressure controlling part, established the spectrophotometry method to measure the total nitrogen and phosphorus in constructed wetland plants. The effects of the ratio of H<inf>2</inf>SO<inf>4</inf> and H<inf>2</inf>O<inf>2</inf> in this system and the digestion time were discussed. The perfect conditions of microwave digestion were found out to this procedure. The optimum parameters for the closed vessel microwave digestion system were that the reagent was the mixture of H<inf>2</inf>SO<inf>4</inf> and H<inf>2</inf>O<inf>2</inf>, the ratio of volume between H<inf>2</inf>SO<inf>4</inf> and H<inf>2</inf>O<inf>2</inf> was 2∶ 1, the ratio between solid quality and liquid volume was 1∶ 45 and the digestion time was 10 minutes. Under this optimum condition, parallel experiments were completed. The methods and results of microwave digestion were also compared with traditional digestion. This method consumes few reagents, is simple and easy to use and causes less pollution. This method was used to determine the amount of TN and TP in the plant samples and the precision and accuracy are satisfactory.